Nonaqueous electrolyte batteries including a negative electrode including a lithium metal, lithium alloy, lithium compound, or carbonaceous material are expected as high energy density batteries, and intensively studied and developed. Lithium ion batteries including a positive electrode containing LiCoO2 or LiMn2O4 as an active material, and a negative electrode containing a carbonaceous material which absorbs and releases lithium ions are widely used in mobile devices.
On the other hand, when mounted on cars such as automobiles and trains, the components of the positive and negative electrodes preferably have high chemical and electrochemical stability, strength, and corrosion resistance, thereby providing high storage performance, cycle performance, and long-term reliability of high output at high temperatures (60° C. or higher). Furthermore, high power performance and long cycle life performance at low temperatures (cold climate areas) such as −40° C. may be demanded.
On the other hand, for improving safety performance of nonaqueous electrolytes, incombustible and nonvolatile electrolytic solutions are under development, but they are not still in actual use because they can deteriorate the output properties, low temperature performance, and long life performance. In addition, when mounted on a car or the like, a lithium ion battery is difficult to replace a lead storage battery mounted on the engine room of the car, and has problem with high temperature durability.
In a lithium ion battery, if the thickness of the negative electrode is decreased to increase the density for increasing the output and capacity, the collector has insufficient strength, so that the battery capacity, output performance, cycle life, and reliability may be markedly limited. In addition, if the particle size of the negative electrode active material is increased in place of decreasing the thickness of the negative electrode, the interface resistance of the electrode increases, which makes it more difficult to exploit high performance. In particular, at low temperatures (for example, −20° C. or lower), the rate of utilization of the active material decreases and discharge is difficult.